Re: [Paddlewise] GPS failure

From: WILA X <WILAX_at_aol.com>
Date: Fri, 22 May 1998 22:37:55 EDT
Lithium batteries has become the generic word for "internal backup batteries".
It may or may not actually be lithium based.  Whatever it is, a reputable GPS
manufacturer should be using batteries with an operating life of 4 to 7 years.
Typically, this battery is soldered to the main receiver board and is not user
replacable.  In addition to saving your waypoints, last position, setup data
(knots vs MPH etc.) the battery saves GPS almanac data.  When you turn the GPS
on it looks at your old almanac data and does a sky search based upon where it
thinks it is.  If you havn't moved more than 100 miles or so from the position
that it last had, and your almanac is less than 30 days old, you usually get a
fix within a minute.  If the battery dies and the GPS can't retain data, you
may see a 20-60 minute delay before it can start giving you position.
Any battery guages are relative readings of the main operating batteries.
There is really no way to check your internal backup battery.
So much for science....
It is kinda fun to run a couple types of navigation simultaneously ie.
compass/chart/DR/GPS.   Really feels good when all solutions work out
properly.  Thats real navigating!
TM  
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Received on Fri May 22 1998 - 19:38:53 PDT

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